The invention relates to novel substituted 3-thiazolines (isothiazolines), processes for their preparation and their use as a flavoring for foods and drinks.
In the flavor industry, there is still a strong demand for compounds which give foods and drinks an olfactory impression such as that formed in the thermal treatment during the cooking, baking and roasting treatment of foods. The resultant aromatizing compounds have especially roasted flavor notes. Compounds of this type have hitherto been only scarcely available for industrial use.
The most important reaction which proceeds during the thermal treatment of foods is the reaction between reducing sugars and amino acids, which is termed the Maillard reaction. During this Maillard reaction, flavorings, particularly, heterocyclic substances, are formed. These compounds contain one or more heteroatoms, such as sulphur, nitrogen and oxygen, various side chains and are aromatic or partially hydrogenated.
In the 2-thiazoline class of substances, especially 2-acetyl-2-thiazoline is a known and industrially used flavoring which is used, owing to its flavor properties, in particular, where roasted flavor properties are desired. Thus, 2-acetyl-2-thiazoline is used, for example, for chicken flavors, where it imparts the typical roasted flavor. The threshold value for this 2-thiazoline is reported in the literature at 0.016 to 0.022 ng/l in air (M. Rychlik, P. Schieberle, W. Grosch, Compilation of Odor Thresholds, Odor Qualities and Retention Indices of Key Food Odorants, Deutsche Forschungsanstalt fxc3xcr Lebensmittelchemie und Institut fur Lebensmittelchemie der Technischen Universitxc3xa4t Muinchen, Garching, 1998). The threshold value is taken to mean the lowest concentration at which a compound can be detected by sensory means.
The present invention provides for a 4-alkanoyl-3-thiazolines of the formula 
where R1, R2 and R3 are identical or different and denote hydrogen or a lower alkyl for use in a flavoring and/or odorant composition.
A lower alkyl denotes an unbranched or branched hydrocarbon having 1 to 3, more preferably 1 or 2, carbon atoms.
The thiazolines of the invention, in particular, 4-acetyl-3-thiazoline, surprisingly have very low threshold values. For example, the 4-acetyl-3-thiazoline (R1,R2,R3xe2x95x90H) of the present invention has a threshold value which is 0.005 ng/l in air. This threshold value is, thus, markedly lower than the case for 2-acetyl-2-thiazoline. The compound 4-acetyl-3-thiazoline is, thus, one of the most aroma-intensive compounds.
4-Acetyl-3-thiazoline was identified in a reaction mixture of fructose as the amino acid 4-carboxy-3-thiazolidine (Example 1).
The compound was identified by fractionating the extract from the reaction mixture by multi-dimensional gas chromatography and subsequent mass-spectrometric analysis. 4-Acetyl-3-thiazoline was unambiguously identified by comparison with the analytical data of an authentic sample.
In addition, systematic experiments were also carried out using a cbromatographic method which is termed gaschromatography-olfactometry (GC-O). In this method, the compounds separated during the chromatographic process are sniffed individually using the nose at the end of the capillary column.
Using these methods, the olfactory and gustatory qualities of 4-acetyl-3-thiazoline were determined.
4-Acetyl-3-thiazoline smells and tastes like popcorn and bread crust and has intensely roasted aroma properties.
The structure of the thiazolines of the present invention was demonstrated by comparison with synthesized 4-acetyl-3-thiazoline. 4-Acetyl-3-thiazoline can be prepared starting from diacetyl. Diacetyl is first brominated. The resultant bromodiacetyl is converted by sodium hydrogen sulphide into 1-mercaptodiacetyl. After reaction with formaldehyde solution and ammonia solution and also chromatographic purification, 4-acetyl-3-thiazoline is obtained (Example 2).
The compounds of the invention, because of their excellent organoleptic character, are particularly suitable as odorants and flavorings for use in flavoring compositions and reaction flavors. It is particularly surprising that the 4-acetyl-3-thiazoline imparts to the compositions a highly intense popcorn-like roasted note at extremely low concentrations.
In flavor compositions, the amount of the inventive compound used is preferably between 0.0005 and 1% by weight, in particular between 0.001 and 0.5% by weight, based on the total composition. Flavor compositions of this type can be used in the entire food and drink sector. In particular, they are suitable for aromatizing snacks, soups, sauces, instant meals, fat compositions, bakery products, yogurt, ice cream and confectionery. The dosage of flavor compositions of this type is preferably 0.005 to 2% by weight, and more preferably between 0.01 and 1% by weight, based on the final food or drink.
The flavors can be used in a liquid form, a spray-dried form or an encapsulated form. Whereas, in liquid form, they are used in a solvent which is customary in practice, such as ethanol, propylene glycol, vegetable oil triglycerides or triacetin. The dry flavors are produced by spray-drying or by encapsulation according to one of the processes which are conventional in the flavor industry. These are, in particular, extrusion and spray granulation.